From Saudi Arabia to Iran, Moscow to Washington and beyond, the rising global tensions over the Syrian war could explode in unpredictable ways.

Some strategic games are too complex to be readily modeled, and when we see such games in the real world that’s exactly when we should be the most worried. That’s my immediate reaction to the situation in Syria and environs.

Consider the distinct yet interrelated clashes going on. Not only did the U.S. strike early Saturday at Syria’s chemical weapons facilities after the regime used such weapons against its citizens in Douma. Tensions between Israel and Iran have been escalating. It seems that Israel recently bombed Syria to limit that country’s support of Iran-backed Hezbollah and to send a signal to Iran. There has also been talk that Hezbollah concentrations in Lebanon will lead to another conflict there. The situation in Gaza has heated up again, with Israeli fire against Palestinian demonstrators leading to significant casualties. As a sideshow to these struggles, U.S. President Donald Trump declined to certify that Iran was in compliance with its nuclear accord and may ditch the deal altogether. In Israel, Benjamin Netanyahu’s government faces significant corruption charges.

The situation between Iran and Saudi Arabia has been worsening, and their proxy war in Yemen has assumed greater significance. Yemeni rebels have been firing missiles into Saudi Arabia, and a big hit may eventually get through the missile shield. Saudi Arabia has recently undergone a major shift in power, seeing some mix of a revolution, internal coup and crackdown on dissent.

Other related stories involve a regionally active and untrustworthy Turkish regime, Saudi displeasure at the shift of Qatar into Iran’s orbit, and the possibility that Trump will use a Middle East conflict either to try to show he is tough with Russia or to distract attention from special counsel Robert Mueller’s investigation. By the way, the U.S. is in the midst of restructuring its National Security Council, probably in a more hawkish direction, and there is no confirmed secretary of state. Toss in the recent Russian use of a nerve agent for an attempted assassination in the U.K.

Some historical events are relatively easy to model with game theory: the Cuban Missile Crisis, many of the Cold War proxy wars, the crisis over North Korean nuclear weapons. In those conflicts, the number of relevant parties is small and each typically has some degree of internal cohesion.

To find a situation comparable to the Middle East today, with so many involved countries, and so many interrelationships between internal and external political issues, one has to go back to the First World War, not an entirely comforting thought.

The situation right before that war had many distinct yet related moving parts, including the dissolution of the Ottoman Empire, the imperialist scramble for colonies, the prior Balkan Wars, a rising Germany seeking parity or superiority with Great Britain, an unstable alliance system, an unworkable Austro-Hungarian Empire, and the complex internal politics of Russia, which eventually led to the Bolshevik Revolution.

Chain reactions can cause small events to cascade into big changes

What do we learn from the history of that time? Well, even if the chance of war was high by early 1914, it was far from obvious that the Central Powers’ attack on France, Belgium and Russia would be set off by a political assassination in the Balkans.

Nonetheless, insufficiently complex situations, chain reactions can cause small events to cascade into big changes. In World War I, one goal behind the assassination of Archduke Franz Ferdinand was to break off parts of the Austro-Hungarian Empire into a new Yugoslavia. The empire responded by making some demands on Serbia, which were not heeded, a declaration of war followed, and the alliance system activated broader conflicts across Europe.

If you don’t quite follow how a single assassination, which was not even seen as so important the day it occurred, triggered the death of so many millions, and the destruction of so much of Europe, that is exactly the point. When there is no clear way for observers to model the situation, a single bad event can take on a very large significance and for reasons that are not entirely explicable.

In today’s Middle East, we also have a broadly festering situation across multiple fronts, with many smaller players, lots of internal political struggles and unstable political units, and commitments from some major external powers, including the U.S., Russia, Iran and Turkey. I find that an uncomfortably close analogy with 1914.

Optimists such as Steven Pinker might suggest that today’s situation in the Middle East is more likely to converge into peace, or only limited struggles, than a major war. But this is not just about the most likely outcome, it is also about the expected value of what will happen. Even a small chance of a major escalation probably makes this messy situation the No. 1 issue facing the world right now.

And if you’re grumpy about the inability of social scientists or the news media to explain it to you in simple terms, that is exactly why the situation is so dangerous.